Abstract
Problem statement: Spectrally Efficient Frequency Division Multiplexing (SEFDM) system promises bandwidth savings by multiplexing overlapped non-orthogonal sub-carriers. However, the loss of orthogonality results in increasing the complexity of generation and detection of the signal. In this work, we propose simple framework for the generation of the SEFDM signal based on the Inverse Discrete Fourier Transform (IDFT). Approach: This study further proposes the use of the Discrete Fourier Transform (DFT) as the receiver front end, specifically for extracting the statistics of the signal needed for recovering the transmitted signal. The proposed transmitter designs employ similar building blocks as Orthogonal Frequency Division Multiplexing (OFDM) based systems, hence, would facilitate an easy migration and/or coexistence with OFDMon the transmitter side. Furthermore, the proposed framework may facilitate the IDFT design for any Frequency Division Multiplexed (FDM) signal with arbitrary sub-carriers spacing. Results and Conclusion: The equivalence of the IDFT generated signal and the modulators based signal is proved mathematically, nonetheless, numerical simulations were performed to verify that equivalence and to test for the performance of the digitally generated signal in AWGN channel. Numerical results confirmed the required spectrum compression and Bit Error Rate (BER) performance at a much reduced complexity.
Highlights
Demand from wireless communications has always necessitated a search for techniques to save the precious wireless spectrum
Higher spectral efficiency is achieved by relaxing the orthogonality rule, defined for Orthogonal Frequency Division Multiplexing (OFDM), to allow the carriers to be placed at closer frequency separation
Due to the intercarrier interference in the system linear detection techniques such as Zero Forcing (ZF) and MinimumMean Square Error (MMSE), failed to achieve bit error rates that can compete with todays wireless applications requirements proposed transmitters facilitate the digital generation of the Spectrally Efficient Frequency Division Multiplexing (SEFDM) signal which can be received using receivers structures as in (Rodrigues and Darwazeh, 2003; Kanaras et al, 2008b; 2009)
Summary
In this study we propose simple IDFT implementations to Consider the first SEFDM frame from (1), sampled generate signals with fractional frequency spacing. The IDFT Based SEFDM Transmitter: SEFDM signal is generated using a bank of modulators running at the sub-carriers frequencies. For an N carrier OFDM system, the input symbols are fed into a ρN point IDFT, where ρ is the number of samples per carrier, the outputs of the IDFT are fed into a digital to analogue converter to generate the continuous time domain signal (Weinstein and Ebert, 197; Macedo and Sousa, 1997).
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